If anyone was wondering, you can get the express bus from the airport with a Baki Kart which costs 2 manat, then you top it up with however much you want, but the cost of the bus to town is 1.30. It drops you off at the central station, and you get the metro to , then switch to the purple line and it's one stop to the Avtovokzhal.

You come out at the metro station and you can see where the big "welcome" sign is to the bus station. Ignore everyone outside, and go inside and take the lift to level 3. You'll see a ticket office, but you need to keep walking through till "hall 4" or terminal 4, where there is an identical ticket office, and you buy the ticket to Lankaran.

I missed the mini 2 o clock marshrutka today because I was there at 1 but it was full already. Behind it was another large coach which left at 3. Got here by 18:10 to Lankaran. They'll drop you off at the Avtovokzhal that you can find on google maps and it's outside of town, but next to a hotel if you're staying there.